Vineet Kumar

Vineet Kumar

MSc Thesis[2015]: Tropical Cyclones in the North Indian Ocean in a warming environmentAffiliation: Department of Atmospheric and Space Sciences, University of Pune

Abstract

The impacts of El Niño Southern Oscillation (ENSO) on tropical cyclone activity (frequency) in Arabian Sea during the month of May are studied for the period 1979-2014. The study shows a total of 7 cyclones in Arabian Sea during this period. Earlier studies have shown that cyclone frequencies vary during an El Niño and La Niña event over north Indian Ocean.

Our present study have shown that out of the 7 cyclones 5 have formed when there was La Niña like conditions which shows that La Niña like conditions enhances the frequency of cyclones in Arabian Sea during May. This is mainly because of enhanced westerly flow in south Arabian Sea and anomalous easterly flow in north Arabian Sea which provides favorable conditions for the formation of a cyclonic circulation. During the first epoch of our study period (1979-1996) there was more El Niño like conditions with positive SST anomalies in Niño 3.4 region and only 1 cyclone has formed during this period whereas during the second epoch (1997-2014) there was La Niña like conditions with negative SST anomalies in Nino 3.4 region for major duration of the period and 6 cyclones have formed during the second epoch. The trend analysis shows a decreasing trend in Niño 3.4 region SST during May and trends in ocean and atmospheric circulation pattern also resembles towards La Niña like conditions favoring more cyclones during second epoch of the study period. Trends in relative vorticity, wind shear shows more favorable condition for cyclone to form or sustain in central and west Arabian Sea.